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Message-Id: <20221003070719.448461097@linuxfoundation.org> Date: Mon, 3 Oct 2022 09:11:31 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Maurizio Lombardi <mlombard@...hat.com>, Alexander Duyck <alexanderduyck@...com>, Chen Lin <chen45464546@....com>, Jakub Kicinski <kuba@...nel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: [PATCH 5.10 24/52] mm: prevent page_frag_alloc() from corrupting the memory From: Maurizio Lombardi <mlombard@...hat.com> commit dac22531bbd4af2426c4e29e05594415ccfa365d upstream. A number of drivers call page_frag_alloc() with a fragment's size > PAGE_SIZE. In low memory conditions, __page_frag_cache_refill() may fail the order 3 cache allocation and fall back to order 0; In this case, the cache will be smaller than the fragment, causing memory corruptions. Prevent this from happening by checking if the newly allocated cache is large enough for the fragment; if not, the allocation will fail and page_frag_alloc() will return NULL. Link: https://lkml.kernel.org/r/20220715125013.247085-1-mlombard@redhat.com Fixes: b63ae8ca096d ("mm/net: Rename and move page fragment handling from net/ to mm/") Signed-off-by: Maurizio Lombardi <mlombard@...hat.com> Reviewed-by: Alexander Duyck <alexanderduyck@...com> Cc: Chen Lin <chen45464546@....com> Cc: Jakub Kicinski <kuba@...nel.org> Cc: <stable@...r.kernel.org> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- mm/page_alloc.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5163,6 +5163,18 @@ refill: /* reset page count bias and offset to start of new frag */ nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1; offset = size - fragsz; + if (unlikely(offset < 0)) { + /* + * The caller is trying to allocate a fragment + * with fragsz > PAGE_SIZE but the cache isn't big + * enough to satisfy the request, this may + * happen in low memory conditions. + * We don't release the cache page because + * it could make memory pressure worse + * so we simply return NULL here. + */ + return NULL; + } } nc->pagecnt_bias--;
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